The present invention relates to methods for detecting the end point of plasma etching and to plasma etching devices which are applicable to, for example, production of semiconductor devices.
Plasma etching may be used during the production of semiconductor devices. During plasma etching, the end point is typically detected by emission spectra of plasma. The method for detecting the end point of etching is an application of emission spectroanalysis of the plasma state during the etching operation. Plasma emission is a phenomenon caused by active gas species in the plasma, and studies on the plasma emission have been developed as plasma diagnostic technologies in spectroanalysis. The plasma emission spectra depend on the reactive gas and reaction products in the plasma, hence observation of a change over time in the intensity of a specified wavelength, i.e., the intensity of a specified substance in the plasma, indicates a change in the amount of the reaction products or the active species during the etching.
A general method for actually detecting the end point includes monitoring a change in the intensity of the plasma emission with respect to a specified wavelength through an interference filter or a monochromator, and detecting the end point of the plasma etching by data processing. This method, however, has the following problems: (1) Deterioration of the plasma light receiving window causes a decrease in transmittance of the plasma emission and affects the end point detection. (2) Fluctuation of emission due to unstable plasma significantly affects the end point detection. (3) When the area of the patterning face of the film subjected to plasma etching is significantly small, (that is, in plasma etching of contact holes and via-holes in semiconductor devices), a change in the emission intensity is extremely low; hence the end point is not detected. (4) When etching a new material, a specific wavelength having a change which will allow end point detection must be found. Such a specific wavelength may be not found in some cases.
Japanese Patent Publication No. 5-28895 (and U.S. Pat. No. 4,602,981) discloses another method for detecting the end point which may solve some of the problems of spectroanalysis of the plasma emission. In this technology, the end point is detected by measuring the radiofrequency voltage (RF) of the electrode in the plasma etching apparatus and by detecting the change (if any) in the RF voltage.
One embodiment of the present invention relates to a plasma etching apparatus using a radiofrequency wave. The apparatus includes a radiofrequency generating means for generating the radiofrequency wave and an electrode provided at a position for generating a plasma. The apparatus also includes a radiofrequency propagation means for propagating the radiofrequency wave generated in the radiofrequency generating means. A radiofrequency voltage measuring means is provided in the radiofrequency propagation means for measuring the voltage of the radiofrequency wave propagating through the radiofrequency propagation means. A radiofrequency current measuring means is also provided in the radiofrequency propagation means for measuring the current of the radiofrequency wave propagating through the radiofrequency propagation means. A determination means is provided for determining the end point of the plasma etching on the basis of the voltage and the current.
Another embodiment relates to a method for detecting the end point of plasma etching using a radiofrequency wave. The method includes measuring a voltage and a current of the radiofrequency wave, and then determining the end point of the plasma etching on the basis of the voltage and the current.
In one aspect of certain embodiments, an end point of an plasma etching operation is found by determining the first to change of the voltage and the current.
Still another embodiment relates to a plasma etching apparatus including an RF generator and a plasma formation region between an anode and a cathode. The apparatus also includes a voltage measurement device and a current measurement device.
Yet another embodiment relates to a method for monitoring a plasma etching operation, including monitoring a voltage of an RF signal and monitoring a current of the RF signal. The method also includes determining when a voltage change occurs and determining when a current change occurs.